1. Field of the Invention
The present invention relates to a structure of attaching a rotation-detecting sensor such as a wheel-speed sensor to a rotation-supporting portion of a wheel axle of a motorcar.
2. Description of the Background Art
A motorcar generally incorporates several types of rotation-detecting sensors such as a sensor for detecting the rotation speed of the wheel and a sensor for detecting the number of rotations of the engine. Of these sensors, a wheel-speed sensor is shown in FIG. 5 together with an example of an attaching structure (see FIG. 5 of the published Japanese patent application Tokukaihei 06-308145).
The attaching structure is explained below. An outer cylinder constituting a wheel hub 1 is provided with a rotation-transferring medium B. An inner cylinder 2 is provided with a rotation-detecting sensor (wheel-speed sensor) P through a ring-shaped metallic attaching member 3. The variation in magnetic field due to the rotation of the rotation-transferring medium B is detected by the rotation-detecting sensor P. The detected signal is converted into an electric signal to be sent to the outside.
In the attaching structure of this conventional rotation-detecting sensor P, an attaching hole 4 for the rotation-detecting sensor P is formed in the attaching member 3. The rotation-detecting sensor P is fitted into the attaching hole 4, and a protrusion provided in the attaching hole 4 is fitted into a groove 5 of the rotation-detecting sensor P. Furthermore, the rotation-detecting sensor P is supported by a spring-type supporting member 6.
In addition, another structure has been disclosed (see claim 5 and FIG. 1 of the published Japanese patent application Tokukai 2004-138458). In this case, the rotation-detecting sensor P is fitted into a hole (pocket) of the attaching member 3. The rotation-detecting sensor P is fixed to the attaching member 3 with a resin-molded body that is formed by filling the hole with resin.
This type of wheel rotation portion is subjected to violent vibrations. In order to withstand it, the structure must be firm. However, in the attaching structure shown in FIG. 5, the secure holding of the rotation-detecting sensor P relies on the fitting into the groove 5 and the holding with the spring member 6. Therefore, to achieve a firm structure, the structure must be complicated, increasing the cost. Furthermore, the groove fitting and the holding with a spring have a limitation.
In addition, in the fixing with a resin-molded body disclosed in the foregoing Tokukai 2004-138458, the position of the rotation-detecting sensor P is usually determined by the insertion (fitting-in) of the rotation-detecting sensor P into the attaching hole. Consequently, the size of the attaching hole cannot be large, making it difficult to fill the attaching hole with the resin. As a result, the support of the rotation-detecting sensor P by the resin-molded body is not sufficient. In other words, the fact is that a firm supporting structure is not achieved.
In view of the above circumstances, the present invention intends to make it possible to attach the rotation-detecting sensor firmly with a simple structure.